A powerful bomb exploded inside a courthouse in the northern Greek city of Thessaloniki Friday, sending smoke billowing in the building and wounding one person.
It was the second bombing in two days — after a blast Thursday outside a jail in Athens that also wounded one person — raising concern that a recent crackdown on Greek militant groups could spur a new series of attacks.
Bombings and other militant attacks are frequent in Greece, but they usually occur at night and rarely target buildings during working hours.
Police had evacuated most of the court building after a Greek newspaper and television station received an anonymous call warning that a bomb had been planted in the toilets in the building's basement.
Dozens of people inside the building were seen running out the court moments before the blast.
Lawyer Babis Apostolides said one man sustained leg injuries, and he had transported him to a nearby hospital, where he received stitches.
"The man was bleeding and was in shock ... fortunately he got medical attention quickly and he's OK," Apostolides told private Alpha television.
He said many people inside the building had been reluctant to leave, because bomb hoaxes at the court are common.
"Police were virtually pulling people out ... there were a sense of panic because the blast was very strong and the dust and smoke was terrible."
Police said the blast knocked down some walls inside the building. A police investigator, who asked not to be identified because he is not authorized to talk to the media, described the damage to the lower part of the building as "extensive."
Court officials said the building will be closed Monday and Tuesday.
The attack came less than a day after a powerful bomb exploded Thursday night outside Greece's largest prison, Korydallos, in the Greek capital, Athens. One woman was slightly injured in that blast, cut by flying glass. That blast had also been preceded by a warning call to a newspaper.
There was no immediate claim of responsibility for either attack, but suspicion fell on radical Greek militant groups that have stepped up attacks in recent years and have been targeted in a recent police crack down.
Last month, authorities arrested and charged six people with membership of Greece's most active militant left wing group. The Revolutionary Struggle organization fired a rocket-propelled grenade at the U.S. embassy in Athens in 2007, causing no injuries.
Several suspected members of that group are being held at Korydallos on pretrial detention.